I’ll defer to your superior knowledge on this issue. 1960 seems awfully early.
http://www.enterprise.navy.mil/About_the_Big_E.htm
http://www.hazegray.org/worldnav/usa/surface.htm#cv
The Enterprise was based on contemporary conventional carriers, with 8 submarine reactors substituted for the conventional boilers.
On the other hand, Kennedy was supposed to be nuclear with what has become a more standard reactor setup, but the idiots in the White House decided to make it conventional.
Both the Kennedy and the Enterprise completed major overhauls in 1995.